Wireless power system with interference avoidance

ABSTRACT

A wireless power system may use a wireless power transmitting device to transmit wireless power to a wireless power receiving device. The wireless power transmitting device may transmit wireless power at a wireless power transmission frequency. Wireless power signals at the wireless power transmission frequency can create interference with a sensitive electrical component in the wireless power receiving device when the wireless power transmission frequency lies in a sensitive frequency band associated with the component. Measurement circuitry in the wireless power receiving device can measure the wireless power transmission frequency. In response to determining that the wireless power transmission frequency lies in a sensitive frequency band, the wireless power receiving device may send an in-band wireless power level adjustment request to the wireless power transmitting device. The request causes a frequency adjustment that moves the wireless power transmission frequency out of the sensitive band.

This application claims the benefit of provisional patent applicationNo. 62/551,711, filed on Aug. 29, 2017, which is hereby incorporated byreference herein in its entirety.

FIELD

This relates generally to power systems, and, more particularly, towireless power systems for charging electronic devices.

BACKGROUND

In a wireless charging system, a wireless charging mat wirelesslytransmits power to a portable electronic device that is placed on themat. The portable electronic device has a receiving coil and rectifiercircuitry for receiving wireless alternating-current (AC) power from acoil in the wireless charging mat that is overlapped by the receivingcoil. The rectifier converts the received AC power into direct-current(DC) power.

SUMMARY

A wireless power system may use a wireless power transmitting device totransmit wireless power to a wireless power receiving device. Thewireless power transmitting device may transmit the wireless power at awireless power transmission frequency. Wireless power signals at thewireless power transmission frequency can create interference when thewireless power transmission frequency lies in a sensitive frequency bandassociated with the sensitive electrical component. The sensitiveelectrical component may be, for example, an image sensor, a touchsensor, a force sensor, or a display.

Measurement circuitry in the wireless power receiving device can measurethe wireless power transmission frequency. In response to determiningthat the wireless power transmission frequency lies in a sensitivefrequency band, the wireless power receiving device may send an in-bandwireless power level adjustment request to the wireless powertransmitting device. The request directs the wireless power transmittingdevice to adjust a wireless power transmission level associated with thetransmitted wireless power and indirectly causes the wireless powertransmitting device to adjust the frequency of the wireless powersignals to avoid the sensitive frequency band.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of an illustrative wireless chargingsystem that includes a wireless power transmitting device and a wirelesspower receiving device in accordance with an embodiment.

FIG. 2 is a circuit diagram of illustrative wireless power transmittingcircuitry and illustrative wireless power receiving circuitry inaccordance with an embodiment.

FIG. 3 is a top view of an illustrative wireless power transmittingdevice in accordance with an embodiment.

FIG. 4 is a top view of an illustrative lower layer of eight coils forthe wireless power transmitting device of FIG. 3 in accordance with anembodiment.

FIG. 5 is a top view of an illustrative middle layer of seven coils forthe wireless power transmitting device of FIG. 3 in accordance with anembodiment.

FIG. 6 is a top view of an illustrative upper layer of seven coils forthe wireless power transmitting device of FIG. 3 in accordance with anembodiment.

FIG. 7 is a graph of an illustrative relationship between wireless powertransmission level and wireless power transmission frequency for awireless power transmitting device in accordance with an embodiment.

FIG. 8 is a flow chart of illustrative operations involved intransmitting wireless power in a wireless power system while avoidingsensitive frequency bands associated with electrical components in awireless power receiving device in accordance with an embodiment.

DETAILED DESCRIPTION

A wireless power system has a wireless power transmitting device such asa wireless charging mat. The wireless power transmitting devicewirelessly transmits power to a wireless power receiving device such asa wristwatch, cellular telephone, tablet computer, laptop computer, orother electronic equipment. The wireless power receiving device usespower from the wireless power transmitting device for powering thedevice and for charging an internal battery.

The wireless power transmitting device has wireless power transmittingcoils arranged under a charging surface. During operation, the wirelesspower transmitting coils are used to transmit wireless power signalsthat are received by a wireless power receiving coil in the wirelesspower receiving device. Wireless power signals are transmitted at awireless power transmission frequency such as a frequency of about 128kHz, frequencies in a range between 100 kHz and 200 kHz, or othersuitable frequency.

To ensure that the amount of power that is transmitted between thewireless power transmitting device and the wireless power receivingdevice is satisfactory, power transmission may be regulated dynamically.In some examples, a wireless power receiving device periodically sendswireless power level adjustment requests to the wireless powertransmitting device. These requests direct the wireless powertransmitting device to increase or decrease the amount of wireless powerbeing transmitted. In some examples, the wireless power transmittingdevice changes the wireless power transmission frequency as part ofadjusting the wireless power transmission level in the wireless powersystem. In some embodiments, a wireless power receiving device leveragesthis ability to affect the wireless power transmission frequency viawireless power adjustment level requests to help avoid undesiredinterference between the wireless power signals and sensitive circuitryin the wireless power receiving device.

An illustrative wireless power system (wireless charging system) isshown in FIG. 1. As shown in FIG. 1, wireless power system 8 includes awireless power transmitting device such as wireless power transmittingdevice 12 and includes a wireless power receiving device such aswireless power receiving device 24. Wireless power transmitting device12 includes control circuitry 16. Wireless power receiving device 24includes control circuitry 30. Control circuitry in system 8 such ascontrol circuitry 16 and control circuitry 30 is used in controlling theoperation of system 8. This control circuitry includes processingcircuitry associated with microprocessors, power management units,baseband processors, digital signal processors, microcontrollers, and/orapplication-specific integrated circuits with processing circuits. Theprocessing circuitry implements desired control and communicationsfeatures in devices 12 and 24. For example, the processing circuitry maybe used in determining power transmission levels, processing sensordata, processing user input, handling communications between devices 12and 24 (e.g., sending and receiving in-band and out-of-band data),selecting wireless power transmitting coils, and otherwise controllingthe operation of system 8. If desired, control circuitry in system 8 maybe used to authorize components to use power and ensure that componentsdo not exceed maximum allowable power consumption levels.

Control circuitry in system 8 may be configured to perform operations insystem 8 using hardware (e.g., dedicated hardware or circuitry),firmware and/or software. Software code for performing operations insystem 8 is stored on non-transitory computer readable storage media(e.g., tangible computer readable storage media) in control circuitry 8.The software code may sometimes be referred to as software, data,program instructions, instructions, or code. The non-transitory computerreadable storage media may include non-volatile memory such asnon-volatile random-access memory (NVRAM), one or more hard drives(e.g., magnetic drives or solid state drives), one or more removableflash drives or other removable media, or the like. Software stored onthe non-transitory computer readable storage media may be executed onthe processing circuitry of control circuitry 16 and/or 30. Theprocessing circuitry may include application-specific integratedcircuits with processing circuitry, one or more microprocessors, acentral processing unit (CPU), digital signal processing circuits,baseband processors, power management units with processing circuitry,microcontrollers, and other processing circuitry.

Power transmitting device 12 may be a stand-alone power adapter (e.g., awireless charging mat that includes power adapter circuitry), may be awireless charging mat that receives power from a power adapter or otherequipment using a cable, may be a portable device, may be equipment thathas been incorporated into furniture, a vehicle, or other system, or maybe other wireless power transfer equipment. Illustrative configurationsin which wireless power transmitting device 12 is a wireless chargingmat may sometimes be described herein as an example.

Power receiving device 24 may be a portable electronic device such as awristwatch, a cellular telephone, a laptop computer, a tablet computer,or other electronic equipment. Power transmitting device 12 may receivepower from a wall outlet (e.g., alternating current), may have a batteryfor supplying power, and/or may have another source of power. Powertransmitting device 12 may have an AC-DC power converter such as powerconverter 14 for converting AC power from a wall outlet or other powersource into DC power. DC power may be used to power control circuitry16. During operation, a controller in control circuitry 16 may use powertransmitting circuitry 52 to transmit wireless power to power receivingcircuitry 54 of device 24. Power transmitting circuitry 52 may haveswitching circuitry (e.g., inverter circuitry 60 formed fromtransistors) that is turned on and off at an alternating-currentwireless power transmission frequency based on control signals providedby control circuitry 16. This creates AC current signals through one ormore coils 42. Coils 42 may be arranged in a planar coil array (e.g., inconfigurations in which device 12 is a wireless charging mat).

As AC currents pass through one or more coils 42, alternating-currentelectromagnetic fields (signals 44) are produced that are received byone or more corresponding coils such as coil 48 in power receivingdevice 24. When the alternating-current electromagnetic fields arereceived by coil 48, corresponding alternating-current currents areinduced in coil 48. Rectifier circuitry such as rectifier 50, whichcontains rectifying components such as synchronous rectificationmetal-oxide-semiconductor transistors arranged in a bridge network,converts received AC signals (received alternating-current signalsassociated with electromagnetic signals 44) from coil 48 into DC voltagesignals for powering device 24.

The DC voltages produced by rectifier 50 can be used in powering abattery such as battery 58 and can be used in powering other componentsin device 24. For example, device 24 may include input-output devices 56such as a display, touch sensor, force sensor, communications circuits,audio components, sensors, and other components and these components maybe powered by the DC voltages produced by rectifier 50 (and/or DCvoltages produced by battery 58).

Device 12 and/or device 24 may communicate wirelessly using in-band orout-of-band communications. Device 12 may, for example, have wirelesstransceiver circuitry 40 that wirelessly transmits out-of-band signalsto device 24 using an antenna. Wireless transceiver circuitry 40 may beused to wirelessly receive out-of-band signals from device 24 using theantenna. Device 24 may have wireless transceiver circuitry 46 thattransmits out-of-band signals to device 12. Receiver circuitry inwireless transceiver 46 may use an antenna to receive out-of-bandsignals from device 12.

Wireless transceiver circuitry 40 uses one or more coils 42 to transmitin-band signals to wireless transceiver circuitry 46 that are receivedby wireless transceiver circuitry 46 using coil 48. Any suitablemodulation scheme may be used to support in-band communications betweendevice 12 and device 24. In some embodiments, frequency-shift keying(FSK) is used to convey in-band data from device 12 to device 24 andamplitude-shift keying (ASK) is used to convey in-band data from device24 to device 12. Power is conveyed wirelessly from device 12 to device24 during these FSK and ASK transmissions.

During wireless power transmission operations, circuitry 52 supplies ACdrive signals to one or more coils 42 at a given power transmissionfrequency. The power transmission frequency may be, for example, apredetermined frequency of about 128 kHz, at least 80 kHz, at least 100kHz, less than 500 kHz, less than 300 kHz, less than 200 kHz, 100-200kHz, 50-200 kHz, 100-200 kHz, or other suitable wireless powerfrequency. In some configurations, device 12 varies power transmissionfrequency based on the power requirements of device 24. In someconfigurations, the device 12 transmits power at a fixed powertransmission frequency, or a frequency that is at least nominally fixedin that device 12 would not change power transmission frequency inresponse to receiver power requirements.

In embodiments that support FSK in-band communications, wirelesstransceiver circuitry 40 uses FSK modulation to modulate the powertransmission frequency of the driving AC signals that device 12 is usingto transmit wireless power and thereby modulates the frequency ofsignals 44. In device 24, coil 48 is used to receive signals 44. Powerreceiving circuitry 54 uses the received signals on coil 48 andrectifier 50 to produce DC power. At the same time, wireless transceivercircuitry 46 uses FSK demodulation to extract the transmitted in-banddata from signals 44. This approach allows FSK data (e.g., FSK datapackets) to be transmitted in-band from device 12 to device 24 withcoils 42 and 48 while power is simultaneously being wirelessly conveyedfrom device 12 to device 24 using coils 42 and 48.

In embodiments that support ASK in-band communications, wirelesstransceiver circuitry 46 transmits in-band data to device 12 by using aswitch (e.g., one or more transistors in transceiver 46 that areconnected to coil 48) to modulate the impedance of power receivingcircuitry 54 (e.g., coil 48). This, in turn, modulates the amplitude ofsignal 44 and the amplitude of the AC signal passing through coil(s) 42.Wireless transceiver circuitry 40 monitors the amplitude of the ACsignal passing through coil(s) 42 and, using ASK demodulation, extractsthe transmitted in-band data from these signals that was transmitted bywireless transceiver circuitry 46. The use of ASK communications allowsASK data bits (e.g., ASK data packets) to be transmitted in-band fromdevice 24 to device 12 with coils 48 and 42 while power issimultaneously being wirelessly conveyed from device 12 to device 24using coils 42 and 48.

Control circuitry 16 has external object measurement circuitry 41(sometimes referred to as foreign object detection circuitry or externalobject detection circuitry) that detects external objects on a chargingsurface associated with device 12. Circuitry 41 can detect foreignobjects such as coils, paper clips, and other metallic objects and candetect the presence of wireless power receiving devices 24. Controlcircuitry 30 has measurement circuitry 43. Measurement circuitry 41 and43 may be used in making inductance measurements (e.g., measurements ofthe inductances of coils 42 and 48), input and output voltagemeasurements (e.g., a rectifier output voltage, and inverter inputvoltage, etc.), current measurements, capacitance measurements,frequency measurements (e.g., measurements of the frequency of wirelesspower signals), and/or other measurements on the circuitry of system 8.Illustrative circuitry of the type that may be used for forming powertransmitting circuitry 52 and power receiving circuitry 54 of FIG. 1 isshown in FIG. 2.

As shown in FIG. 2, power transmitting circuitry 52 may include drivecircuitry such as inverters 60 that supply drive signals at the wirelesspower transmission frequency to respective wireless power transmitterresonant circuits. Each wireless power transmitter resonant circuit mayinclude a wireless power transmitting coil 42 and capacitor 70.Rectifier 50 in wireless power receiving circuitry 54 receives wirelesspower signals using a wireless power receiver resonant circuit thatincludes capacitor 74 and wireless power receiving coil 48.

Inverters 60 have metal-oxide-semiconductor transistors or othersuitable transistors that are modulated by AC control signals fromcontrol circuitry 16 (FIG. 1) that are received on respective controlsignal inputs 62. The attributes of each AC control signal (e.g., dutycycle, frequency, etc.) may be adjusted by control circuitry 16dynamically during power transmission to control the amount of powerbeing transmitted by power transmitting coils 42.

When transmitting wireless power, control circuitry 16 (FIG. 1) selectsone or more appropriate coils 42 to use in transmitting signals 44 tocoil 48 (e.g., control circuitry 16 supplies control signals to theinputs 62 of the inverters 60 that are to drive the selected coils toproduce signals 44). Coil 48 and capacitor 74 form a resonant circuit incircuitry 54 that receives signals 44. Receiver 50 rectifies thereceived signals and provides direct-current output power at output 68.

A top view of an illustrative configuration for device 12 in whichdevice 12 has an array of coils 42 is shown in FIG. 3. Device 12 may, ingeneral, have any suitable number of coils 42 (e.g., 22 coils, at leastone coil, at least 2 coils, at least 3 coils, at least 5 coils, at least7 coils, at least 10 coils, at least 15 coils, fewer than 30 coils,fewer than 50 coils, etc.). Coils 42 may be arranged in rows and columnsand may or may not partially overlap each other. In the example of FIG.3, coils 42 partially overlap each other and arranged in three layers.

Device 12 may have a housing 78 (e.g., a housing formed from plastic orother materials) that forms a planar housing surface that covers coils42 (sometimes referred to as a charging surface). One or more wirelesspower receiving devices such as device 24 may be positioned on thecharging surface to receive wireless power from coils 42. Coils 42 maybe circular or may have other suitable shapes (e.g., coils 42 may besquare, may have hexagonal shapes, may have other shapes havingrotational symmetry, etc.). In the illustrative configuration of FIG. 3,coils 42 are circular and are formed from multiple wire turns (e.g.,multiple turns formed from metal traces, bare wire, insulated wire, wiremonofilaments, multifilament wire, etc.).

FIGS. 4, 5, and 6 are diagrams of illustrative layers of coils 42 in awireless power transmitting device such as a charging mat having 22coils in three layers.

FIG. 4 is a top view of an illustrative configuration for a lower layerhaving eight coils 42 in wireless power transmitting device 12 of FIG.3. FIG. 5 is a top view of an illustrative configuration for a middlelayer having seven coils 42 for wireless power transmitting device 12 ofFIG. 3. FIG. 6 is a top view of an illustrative configuration for anupper layer having seven coils for wireless power transmitting device 12of FIG. 3. In this example, the lower layer has 8 coils, the middlelayer has 7 coils, and the upper layer has 7 coils. In general, eachlayer may have any suitable number of coils (e.g., at least 2 coils, atleast 5 coils, fewer than 9 coils, fewer than 14 coils, 6-9 coils,etc.). Device 12 may have one layer of coils 42, at least two layers ofcoils 42, at least three layers of coils 42, at least four layers ofcoils 42, fewer than five layers of coils 42, 4-6 layers of coils, etc.Configurations in which device 12 has only a single coil 42 may also beused.

Device 24 may contain circuitry that is sensitive to radio-frequencysignal interference. This circuitry may include, for example,input-output devices 56 such as a display, a touch sensor (e.g., atwo-dimensional capacitive touch sensor) overlapping the display, aradio (e.g., an amplitude modulation radio), a force sensor, digitalimage sensors (e.g., infrared and/or visible light image sensors forcomponents such as cameras, etc.), and/or other sensitive circuitry.During wireless power transmission, the wireless power signals 44 thatare transmitted to device 24 can directly interfere with the sensitivecircuitry and/or can interfere with the sensitive circuitry bygenerating interfering signal harmonics. For example, some touch sensorsdo not sense touches properly when subjected to radio interference andsome force sensors do not sense force input properly when subjected toradio interference. For example, some displays do not display framesconsistently (e.g., images appear wavy) when subjected to radiointerference.

To prevent disruption to the operation of device 24 as wireless powersignals are being transmitted by device 10, device 24 can becharacterized using testing equipment (e.g., during manufacturing). Thetesting equipment can supply signals 44 over a range of potentialoperating frequencies while the performance ofradio-frequency-interference-sensitive components in device 24 ismonitored. Frequency bands in which undesired interference effects aredetected can be identified. Information on these frequency bands (whichmay sometimes be referred to as disallowed frequency bands, sensitivefrequency bands, interference-producing frequency bands, etc.) such asstart and end frequencies for the frequency bands may be stored inmemory in device 24. During wireless power transfer operations, device24 can measure the wireless power transmitting frequency in use, cancompare this measured frequency to the stored sensitive frequency bands,and can take action to avoid use (or at least to avoid prolonged use) ofwireless power signals with frequencies in the sensitive frequencybands.

In systems in which the frequency of power transmitting circuitry 52 canbe adjusted in response to frequency adjustment commands from device 24,device 24 can send frequency adjustment commands to device 12 wheneverpower is being transmitted at a wireless power transmission frequencythat falls within a sensitive frequency band. In some configurations,however, device 12 may not support the use of frequency adjustmentcommands.

To prevent interference in scenarios in which device 12 does not supportfrequency adjustment commands, device 24 can transmit power adjustmentcommands to device 12 that indirectly cause device 24 to adjust itswireless power transmission frequency.

Consider, as an example, the scenario illustrated in FIG. 7. In FIG. 7,the output power P of an illustrative wireless power transmitting devicesuch as device 12 has been plotted as a function of wireless powertransmission frequency f (curve 80). Illustrative sensitive frequencybands associated with an illustrative wireless power receiving device(e.g., sensitive frequency band 84 extending from frequency fa tofrequency fb and sensitive frequency band 82 extending from frequency fcto frequency fd) are also plotted in FIG. 7. When device 12 transmitswireless power at a frequency f that lies outside of bands 84 and 82(and within permitted frequency range f1 to f2, which may be, forexample, 100 kHz to 200 kHz or other suitable permitted frequencyrange), device 24 operates within design tolerances, for example, in itsability to sense input and provide output. However, when device 12transmits wireless power at a frequency f that lies within one ofsensitive bends 84 and 82, the transmitted wireless power signalsinterfere with the operation of device 12. For example, images displayedon a display in device 24 will contain undesired visual artifacts, touchsensor or force sensor measurements will contain excessive noise, thereception of wireless communications signals (e.g., cellular or WiFi)will be adversely affected, and/or sensitive components such as digitalimage sensors will not be able to capture satisfactory images.

During operation, wireless power receiving device 24 may require varyingamounts of wireless power. When an increase in power is desired,wireless power receiving device 24 transmits a wireless power adjustmentrequest (e.g., a wireless power adjustment command) that requests andthereby causes device 12 to increase its transmitted power level. Device24 can issue wireless power adjustment requests that cause device 12 todecrease the amount of wireless power being transmitted when device 24desires to receive less power from device 12. Device 12 may satisfythese power adjustment requests by using control circuitry 16 to adjustthe drive signals provided to the inverter circuitry in device 12 andthereby adjust the properties of wireless power signals 44. Notably,device 12 adjusts the wireless power transmission frequency f that isassociated with the drive signals for inverter circuitry 60 and that isassociated with wireless power signals 44 in accordance with curve 80.In exemplary curve 80, when less power is required, frequency f isadjusted upwards. When more power is required, frequency f can belowered.

Device 24 can use measurement circuitry 43 to measure the frequency f ofthe wireless power signals that are being received by wireless powerreceiving circuitry 54. Whenever frequency f overlaps a sensitivefrequency band such as band 84 and band 82 of FIG. 7, device 24 can useASK in-band communications and/or other wireless communications totransmit a wireless power level adjustment request to device 12. Thewireless power level adjustment request directs device 12 to adjust theamount of wireless power being transmitted and indirectly causes thewireless power transmission frequency to be adjusted out of thesensitive band. If, as an example, it is determined that wireless powersignals are being transmitted at a frequency associated with operatingpoint 86 in sensitive band 82, device 24 can transmit a wireless poweradjustment request to device 12 that requests that device 24 increaseits wireless power transmission level. In response, device 12 maytransition from transmitting wireless power at the power and frequencyassociated with point 86 to a higher power (and therefore lowerfrequency) associated with operating point 88. The wireless powertransmission frequency at operating point 88 is a safe frequency that isoutside sensitive frequency band 82, so interference with the operationof components of device 24 is avoided.

FIG. 8 is a flow chart of illustrative operations associated withoperating system 8 while preventing undesired interference between thewireless power signal transmitted by device 12 and the operation ofsensitive components in device 24.

During the operations of block 90, device 12 transmits wireless powersignals 44 at wireless power transmission frequency f and power P.Wireless power receiving device 24 receives the transmitted signalsusing power receiving circuitry 54 while using measurement circuitry 43or other suitable circuitry in device 24 to measure the frequencyassociated with the transmitted wireless power signals. The frequency fmay be compared to the known (stored) sensitive frequency bands (e.g.,bands 82 and 84 in the example of FIG. 7). So long as the frequency f ofthe wireless power signals lies outside of the sensitive bands, wirelesspower can be transmitted normally. During these normal operations,device 24 may occasionally issue wireless power level adjustmentcommands according to the time-varying power needs of device 24. Due toadjustments made by device 12 and/or changes made by device 12 inresponse to normal wireless power level adjustment commands receivedfrom device 24, the wireless power transmitting frequency f may moveinto a sensitive frequency band.

When operation in a sensitive frequency band is detected by device 24(e.g., by wireless-power-transmission-frequency measurement circuitrysuch as circuitry 43), device 24 may take corrective action. In someexamples, during the operations of block 92, device 24 may determinewhether the wireless power transmission frequency should be adjusted upor down. Device 24 may, as an example, determine that the wireless powertransmission frequency should be moved towards the closest edge of thesensitive band. As an example, the wireless power frequency may belowered to avoid operating in band 82 in scenarios in which theoperating frequency for device 12 lies within band 82 close to lowerfrequency fc and may be raised to avoid operating in band 82 inscenarios in which the operating frequency for device 12 lies withinband 82 close to upper frequency fd. In some examples, device 24determines that the last frequency change was a change in a particularup or down direction, and again moves the frequency in the samedirection.

During the operations of block 94, device 24 may determine how much thewireless power level P should be adjusted in the power level adjustmentrequest (e.g., device 24 may determine a desired value of power leveladjustment ΔP) and may supply a corresponding wireless power adjustmentrequest to device 12 (e.g., using in-band communications such as ASKdata transmission between device 24 and device 12). The value of ΔP maybe determined by computing a fixed fraction (e.g., 10%, 1-15%, 0.01-2%,at least 0.5%, at least 2%, less than 7%, less than 1.5%, or othersuitable amount) of the current wireless power level P, may be based onthe size of the sensitive frequency band in which the wireless powertransmission frequency lies (e.g., so that larger bands results inlarger ΔP values), and/or may be based on other suitable criteria (e.g.,the wireless power transmission frequency, the distance of the wirelesspower transmission frequency to the closest sensitive band edge, etc.).Device 24 may also use its wireless power transmission frequencymonitoring circuitry to measure the change in wireless powertransmission frequency that results from the requested change inwireless power transmission level.

In response to determining that the wireless power transmissionfrequency has changed, but still lies within a sensitive frequency band,the operations of blocks 92 and 94 can be repeated to make sure that thewireless power transmission frequency is moved out of the sensitiveband.

In response to determining that the wireless power transmissionfrequency has changed and no longer lies within a sensitive frequencyband, operations may loop back to block 90 (normal operation).

In response to determining that the wireless power transmissionfrequency did not change in response to a given power adjustment requestsent to device 12 or more than a predetermined number of poweradjustment requests send to device 12, device 24 may, if desired disablefrequency avoidance operations (e.g., block 96) for a predeterminedperiod of time, until device 24 pairs with a new wireless powertransmitting device, and/or until other criteria have been satisfied.This may help avoid unnecessary power adjustments in systems in whichpower adjustments are determined to not readily result in frequencyadjustments of the type associated with curve 80 of FIG. 7. In someconfigurations, device 24 may, if desired, change the direction of poweradjustments (and therefore the direction of frequency adjustments) thatare being made in response to determining that attempts to avoid asensitive band are not succeeding. This allows avoidance of a sensitiveband in situations in which the current frequency is at an edge of anallowed frequency band of device 24 and is therefore unable to befurther adjusted in the current direction. In some embodiments, device24 may additionally or alternatively cause a change in operation of asensitive electrical component in response to determining that thewireless power transmission frequency did not change in response to thepower adjustment request sent to device 12. For example, a display framerate may be adjusted, an image sensor frame rate may be adjusted, atouch sensor or force sensor clock may be adjusted, wirelesscommunications frequencies being used to handle a communications sessionmay be adjusted, or other changes may be made.

The foregoing is merely illustrative and various modifications can bemade to the described embodiments. The foregoing embodiments may beimplemented individually or in any combination.

What is claimed is:
 1. A wireless power receiving device configured toreceive wireless power signals transmitted from a wireless powertransmitting device, the wireless power receiving device comprising:wireless power receiving circuitry having a wireless power receivingcoil and rectifier circuitry coupled to the wireless power receivingcoil; wireless power transmission frequency measurement circuitryconfigured to measure the frequency of a wireless power signal receivedat the wireless power receiving coil; an electrical component that issensitive to wireless transmission at a sensitive frequency band; andcontrol circuitry configured to: determine whether the frequency of thewireless power signal received at the wireless power receiving coiloverlaps the sensitive frequency band; and upon determining that thefrequency of the wireless power signal received at the wireless powerreceiving coil overlaps the sensitive frequency band, send a wirelesspower level adjustment request to the wireless power transmittingdevice.
 2. The wireless power transmitting device of claim 1 wherein thecontrol circuitry is configured to determine whether the wireless powerlevel adjustment request includes a request for an increase or for adecrease in wireless power transmission from the wireless powertransmitting device.
 3. The wireless power transmitting device of claim1 wherein the wireless power level adjustment request is associated witha request for an amount of wireless power level change and wherein thecontrol circuitry is configured to determine the amount of wirelesspower level change based at least partly on a size of the sensitivefrequency band.
 4. The wireless power transmitting device of claim 1wherein the wireless power level adjustment request is associated with arequest for an amount of wireless power level change and wherein thecontrol circuitry is configured to determine the amount of wirelesspower level change based at least partly on the frequency of thewireless power signal received at the wireless power receiving coil. 5.The wireless power receiving device of claim 1 wherein the controlcircuitry is configured to at least temporarily disable sending ofwireless power adjustment requests in response to determining that thewireless power level adjustment request resulted in no change in thewireless power transmission frequency.
 6. The wireless power receivingdevice of claim 5, wherein the control circuitry is configured to causea change in operation of the electrical component, in response todetermining that the wireless power level adjustment request resulted inno change in the frequency of the wireless power signal received at thewireless power receiving coil.
 7. The wireless power receiving device ofclaim 1 wherein the electrical component comprises a display.
 8. Thewireless power receiving device of claim 1 wherein the electricalcomponent comprises a touch sensor.
 9. The wireless power receivingdevice of claim 1 wherein the electrical component comprises an imagesensor.
 10. The wireless power receiving device of claim 1 wherein theelectrical component comprises a force sensor.
 11. The wireless powerreceiving device of claim 1 wherein the control circuitry comprisesin-band transmitter circuitry configured to send the wireless powerlevel adjustment request to the wireless power transmitting device. 12.The wireless power receiving device of claim 11 wherein the in-bandtransmitter circuitry comprises an amplitude-shift-keying in-bandtransmitter.
 13. A wireless power receiving device, comprising: wirelesspower receiving circuitry configured to receive wireless power signalsat a wireless power transmission frequency; and control circuitryconfigured to transmit a wireless power transmission level adjustmentrequest based on determining that the wireless power transmissionfrequency lies in a sensitive frequency band.
 14. The wireless powerreceiving device of claim 13 wherein the control circuitry comprises anamplitude-shift-keying transmitter configured to send the wireless powertransmission level adjustment request.
 15. The wireless power receivingdevice of claim 13 further comprising a display, wherein the sensitivefrequency band is associated with interference between the wirelesspower signals at a wireless power transmission frequency in thesensitive frequency band and operation of the display.
 16. The wirelesspower receiving device of claim 13 further comprising a touch sensor,wherein the sensitive frequency band is associated with interferencebetween the wireless power signals at a wireless power transmissionfrequency in the sensitive frequency band and touch detection by thetouch sensor.
 17. The wireless power receiving device of claim 13further comprising a sensor, wherein the sensitive frequency band isassociated with interference between the wireless power signals at awireless power transmission frequency in the sensitive frequency bandand operation of the sensor.
 18. The wireless power receiving device ofclaim 17 wherein the sensor comprises an image sensor.
 19. The wirelesspower receiving device of claim 17 wherein the sensor comprises a forcesensor.
 20. The wireless power receiving device of claim 13 wherein thewireless power receiving circuitry comprises a wireless power receivingcoil and rectifier circuitry coupled to the wireless power receivingcoil.
 21. The wireless power receiving device of claim 13 furthercomprising: wireless power transmission frequency measurement circuitryconfigured to detect a frequency of wireless power signals at thewireless power receiving coil.
 22. A wireless power receiving deviceconfigured to receive wireless power signals transmitted from a wirelesspower transmitting device at a wireless power transmission frequency,comprising: wireless power receiving circuitry configured to receive thewireless power signals, the wireless power receiving circuitrycomprising a wireless power receiving coil; circuitry configured todetect wireless power signals of the wireless power transmissionfrequency at the wireless power receiving coil; control circuitryconfigured to: determine whether the measured wireless powertransmission frequency lies within a sensitive frequency band; and upondetermining that the measured wireless power transmission frequency lieswithin the sensitive frequency band, sending a wireless power leveladjustment request to the wireless power transmitting device that causesthe wireless power transmitting device to adjust a power levelassociated with the wireless power signals and that causes the wirelesspower transmitting device to adjust the wireless power transmissionfrequency out of the sensitive frequency band.
 23. The wireless powerreceiving device of claim 22 further comprising: an electrical componentsubject to interference in the presence of wireless power signals in thesensitive frequency band.
 24. The wireless power receiving device ofclaim 23 wherein the electrical component comprises a component selectedfrom the group consisting of: a display, a touch sensor, and an imagesensor.